I feel compelled to enlighten a few, I have a hard time dealing with the lack of knowledge. First off, a bit of background. I am an operations supervisor at the last grass roots oil refinery built in the USA, 27 years there. We produce about 6 million gallons of gasoline alone a day. I have worked in several areas of the plant, ran a couple DCS consoles, produced lots of fuel, gasoline, diesel, propane, butane, asphalt, fuel oil, ect. Also have hot rodded/raced cars and motorcycles off and on over the years, assembled a few engines, have a pretty good understanding of how an internal combustion engine works, converts or burns fuel to generate horsepower or energy. RON is a measure of octane, Research octane. There also is MON, motor octane. The octane advertised at the pump is RON+MON divided by 2, another words an average of the 2 ratings. RON is the result of our very expensive analyzer analysis, MON is a specialized 1 cylinder engine in the lab where the fuel is run and ignition timing and/or the engine's actual real time compression ratio is varied until the point of detonation to measure and determine the MON result. Generally fuels with a higher RON or octane have slightly less potential energy or BTUs than a lower octane fuel. So, another words if your engine manufacturer says the engine is designed to operate on 87 octane fuel, using 93 will don nothing for you really and may actually result in very slightly lower fuel mileage based on its energy content. Propane has a much higher octane than gasoline and when an engine is converted to burn propane, its mileage drops considerably because propane doesn't have nearly the energy or BTU content of gasoline, less carbon molecules, long chain hydrocarbons in the propane versus typical gasoline. Race fuels with an octane of say 115 burned in a everyday car designed for 87 will return lower mpg than a quality 87 octane fuel.
And about the "valve rattle" crap. Actually when the compression cycle takes place in a 4 cycle engine, the vrod engine for example, and the air/fuel mixture is ignited just before TDC, both the exhaust and intake valves are closed at that time. The exhaust valve is next to open but about 180° of crank rotation after fuel ignition/TDC. Gasoline when ignited in an engine under compression burns very quickly, actually a flame front. When the air fuel mixture detonates versus burn, hence the noise, the so called "valve rattle". The noise is not the valves rattling as they are fully closed and on their seats, but the actual echo of the detonation or explosion within a cylinder, within the engine block and its components. These events are very negative for an engine as the explosive forces try to halt the rising piston before TDC occurs. You see, the fuel ignition or spark plug firing occurs 10-35° before TDC occurs, depending on engine rpm, load and other data references. Sustaining such detonation over time can actually fracture or burn pistons, the rings, cylinder walls, damage the rod and crank bearings. Damage occurs much quicker on forced induction engines, such as turbocharged or supercharged engines, due in part to the higher effective peak cylinder pressures versus a normally aspirated engine, hence the need for higher octane fuel in turbocharged or blown engines to prevent detonation and damage, and why damage can occur so quickly in a blown engine with insufficient fuel octane, or incorrect ignition timing settings or faults, or overly lean air/fuel ratios.
Also, liquid gasoline does not burn, combust, or oxidize. The liquid gasoline must be vaporized either mechanically by the injector, or by heat of combustion. Vapors or gases combust/oxidize, liquids do not.
I could go on and on about the subject and with more detail, but this is getting lengthy. Hope it enlightens someone anyways.
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